Electromagnetic counter

ABSTRACT

In an electromagnetic counter of the type wherein the digit wheel of the counter is operated by the armature of an electromagnet through a ratchet wheel and a pawl, the pawl is made of plastic and is provided with a resilient member engaged by the armature when it is attracted by the electromagnet. The bending strength of the resilient member is determined such that it acts as a rigid member during the operation of the digit wheel but thereafter as a spring thereby resiliently resisting against the movement of the armature toward the core.

Umted States Patent [1 1 1111 3,925,741 Ohtsuka et al. 5] Dec. 9, 1975 [54] ELECTROMAGNETIC COUNTER 2,389,695 11/1945 Stenhammer 74/576 3,504,559 4 1970 Sh J t l.... 74/575 X [75] Inventors ohtsuka Yonezawa; Tosh") 3,540,306 11i1970 74/576 Sat", Yamagata, both of Japan 3,660,642 5/1972 Jullien-Davin 235/92 0 [73] Assignee: Tamura Electric Works, Ltd.,

Tokyo, Japan Primary Examiner-G. Harris Filed: g 1974 Attorney, Agent, or Fzrm-Charles E. Pfund, Esq.

[21] Appl. No.: 501,157 4 57 ABSTRACT In an electromagnetic counter of the type wherein the [30] Foreign Application Priority Data digit wheel of the counter is operated by the armature Aug. 30, 1973 Japan 48-101924 Of an electromagnet through a ratchet Wheel and a pawl, the pawl is made of plastic and is provided with [5 US. Cl 335/140; 74/5 76; 234/92 C a resilient member engaged by the armature when it is [51] Int. Cl. H01H 51/08 attracted y the magn t. Th bending strength [58] Field of Search 74/575, 576 X, 577 R 142; of the resilient member is determined such that it acts 234/92 C; 335/123, 140, 225, 239 as a rigid member during the operation of the digit wheel but thereafter as a spring thereby resiliently re- [56] Ref Cit d sisting against the movement of the armature toward UNITED STATES PATENTS the core- 2,217,074 10/1940 Obergfell 74/576 X 1 Claim, 5 Drawing Figures US. Patent Dec. 9, 1975 3,925,741

APgjrOR F I 11 16.2 Z2? This invention relates to an electromagnetic counter and more particularly to an electromagnetic counter provided with an improved noise preventing device.

In a prior art electromagnetic counter as shown in FIGS. 1 and 2, in order to decrease the stroke of the armature 1 utilized to operate a digit wheel stepwise as shown in FIG. 1. and to decrease the air gap between the armature and core 2 of an electromagnet, the relative dimension of these elements has been proportioned such that the armature 1 engages the core 2 as shown in FIG. 2 when the former is attracted by the latter. When the armature and core perfectly contact with each other over the entire contact area no noise is formed even when the contact area is small. However,

if there is an air gap between the armature and core at the time of attraction the armature 1 vibrates as the magnetic flux pulsates thereby producing noise. But it is difficult to completely eliminate noise because it is impossible to vary the stroke of the armature since the position of the fulcrum of the armature, the length of the core, and configurations of the ratchet wheel and an operating pawl associated with the digit wheel are fixed. Vibration of the armature wears the ratchet wheel and pawl.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide an improved electromagnetic counter capable of reducing the noise.

Another object of this invention is to provide an electromagnetic counter capable of preventing wear of the ratchet wheel and pawl for operating the digit wheel.

According to this invention there is provided an electromagnetic counter of the type wherein a digit wheel is operated by the movement of an armature of an electromagnet through a ratchet wheel and a pawl, characterized in that the pawl is made of plastic and that the pawl is provided with a resilient member engaged by the armature when it is attracted by the electromagnet.

The resilient member has a bending strength which is larger than the force necessary to operate the digit wheel but smaller than the attractive force applied to the armature by the electromagnet. Accordingly, when the electromagnet is energized, the resilient member acts as a rigid member to positively actuate the digit member, but after the actuation of the digit wheel the resilient member operates as a spring so that the movement of the armature is resiliently resisted by the resilient member when the armature engages the core of the electromagnet thus decreasing noise.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing:

FIG. 1 is a diagrammatic side view of a driving device of a prior art electromagnet counter;

FIG. 2 is a partial view showing a manner of engagement of the armature and core of the electromagnetic counter shown in FIG. 1;

FIG. 3 is a front view of one embodiment of the electromagnetic counter embodying the invention;

FIG. 4 is a side view of the electromagnetic couner shown in FIG. 3 and FIG. 5 is an enlarged view showing the coupling be tween the pawl and armature shown in FIg. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the electromagnetic counter of this invention shown in FIGS. 3 and 400mprises a U Shaped frame 6, a pawl 3 pivotally mounted on a pin 4 secured to one leg of the frame 6, an armature 5 having one end coupled to the pawl 3 in a manner to be described later in more detail and the other end received in a notch, not shown, provided for the other leg of the frame, and a spring 7 for biasing the armature 5 in the counterclockwise direction. An electromagnet 1 l is positioned on the lower leg of the yoke 6 and its core 8 is provided with a shading ring, not shown. A plurality of digit wheels 9 are rotatably mounted on the upper portion of the yoke 6 and their driving pawl 10 is driven by pawl 3 in a manner well known in the art. When the coil of the electromagnet 11 is energized, the armature 5 is attracted by the core 8 to step digit wheels by one half digit. Upon de-energization of the electromagnet l l, the armature 5 is pulled away by the spring for stepping digit wheels 9 one half digit.

The coupling between the armature 5 and the pawl 3 is constructed as follows. More particularly, the pawl 3 is in the form of a letter L and its horizontal leg comprises a relatively rigid C shaped portion 12 and a relatively thin resilient portion 13 disposed to cooperate with the C .shaped portion 12 to form a substantially closed window 14 which receives the free end of the armature. According to this invention, the yoke 3 is made of plastic such as nylon and the bending strength of the resilient portion 13 is made to be larger than the force required to step the digit wheels but to be smaller than the pulling force of the core 8 upon the armature 5. Accordingly, as the armature 5 is attracted by the core and engages the resilient portion 13, the portion 13 will not be flexed but acts as a rigid member whereby the pawl is rotated in the clockwise direction as viewed in FIG. 4 for positively stepping one half digit the digit wheels. Thereafter, the digit wheels and the pawl are held stationary so that if there is an air gap still remaining between the armature 5 and core 8, the armature will be attracted further by the core. However, as has been pointed out above, as the bending strength of the resilient portion is made to be smaller than the pulling force of the core, the resilient portion 13 is flexed until the armature engages the core or until the air gap is reduced to zero. In this manner, as the movement of the armature toward the core is resiliently resisted by the resiliency of the resilient portion 13 at the time when the armature engages the core, it is possible to greatly decrease the noise which otherwise would be produced. Furthermore, as the pawl is made of plastic, such as nylon for example, it is not only easy to construct it but also to decrease wear of the ratchet wheel 10 and pawl.

While the invention has been shown and described in terms ofa preferred embodiment thereof it will be clear that the invention is by no means limited to the specific embodiment and that many changes and modifications will readily occur to one skilled in the art without departing from the true spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. In an electromagnetic counter of the type wherein a digit wheel is operated by the movement of an armature of an electromagnet through a ratchet wheel and a plastic pawl, the improvement wherein said pawl comprises a letter L-shaped member, one leg thereof being shaped to actuate said ratchet wheel whereas the other leg being provided with a relatively rigid C-shaped portion and a resilient member, said resilient member engaged by said armature when it is attracted by said electromagnet, said resilient member having a bending strength which is larger than the force necessary to operate said digit wheel but smaller than the attractive force so that the movement of said armature is yieldingly resisted by the resiliency of said resilient member when said armature engages the core of said electromagnet, said C-shaped portion and said resilient member cooperating with each other to define a substantially closed window which receives said armature. 

1. In an electromagnetic counter of the type wherein a digit wheel is operated by the movement of an armature of an electromagnet through a ratchet wheel and a plastic pawl, the improvement wherein said pawl comprises a letter L-shaped member, one leg thereof being shaped to actuate said ratchet wheel whereas the other leg being provided with a relatively rigiD Cshaped portion and a resilient member, said resilient member engaged by said armature when it is attracted by said electromagnet, said resilient member having a bending strength which is larger than the force necessary to operate said digit wheel but smaller than the attractive force so that the movement of said armature is yieldingly resisted by the resiliency of said resilient member when said armature engages the core of said electromagnet, said C-shaped portion and said resilient member cooperating with each other to define a substantially closed window which receives said armature. 